Actor(s): APT31
According to PTSecurity, this RAT uses Yandex Disk as a C2.
rule win_yarat_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2026-01-05" version = "1" description = "Detects win.yarat." info = "autogenerated rule brought to you by yara-signator" tool = "yara-signator v0.6.0" signator_config = "callsandjumps;datarefs;binvalue" malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.yarat" malpedia_rule_date = "20260105" malpedia_hash = "19b79e7cab4eaf532122e5b45a77dd8f6bb5cc79" malpedia_version = "20251219" malpedia_license = "CC BY-SA 4.0" malpedia_sharing = "TLP:WHITE" /* DISCLAIMER * The strings used in this rule have been automatically selected from the * disassembly of memory dumps and unpacked files, using YARA-Signator. * The code and documentation is published here: * https://github.com/fxb-cocacoding/yara-signator * As Malpedia is used as data source, please note that for a given * number of families, only single samples are documented. * This likely impacts the degree of generalization these rules will offer. * Take the described generation method also into consideration when you * apply the rules in your use cases and assign them confidence levels. */ strings: $sequence_0 = { 8b07 51 03f0 52 56 e8???????? 8b8564feffff } // n = 7, score = 100 // 8b07 | mov eax, dword ptr [edi] // 51 | push ecx // 03f0 | add esi, eax // 52 | push edx // 56 | push esi // e8???????? | // 8b8564feffff | mov eax, dword ptr [ebp - 0x19c] $sequence_1 = { 8b7d08 33f6 33db 85ff 7439 8bf7 8d4e01 } // n = 7, score = 100 // 8b7d08 | mov edi, dword ptr [ebp + 8] // 33f6 | xor esi, esi // 33db | xor ebx, ebx // 85ff | test edi, edi // 7439 | je 0x3b // 8bf7 | mov esi, edi // 8d4e01 | lea ecx, [esi + 1] $sequence_2 = { c1ca03 663bf5 84eb 81f21b6f5a16 f7da f5 81fede018b2e } // n = 7, score = 100 // c1ca03 | ror edx, 3 // 663bf5 | cmp si, bp // 84eb | test bl, ch // 81f21b6f5a16 | xor edx, 0x165a6f1b // f7da | neg edx // f5 | cmc // 81fede018b2e | cmp esi, 0x2e8b01de $sequence_3 = { 8b3f 85ff 75d7 837c241c00 8b3d???????? 754f 6804010000 } // n = 7, score = 100 // 8b3f | mov edi, dword ptr [edi] // 85ff | test edi, edi // 75d7 | jne 0xffffffd9 // 837c241c00 | cmp dword ptr [esp + 0x1c], 0 // 8b3d???????? | // 754f | jne 0x51 // 6804010000 | push 0x104 $sequence_4 = { f5 81c702000000 6685f1 0fadc2 f6d0 0f42c5 0fc8 } // n = 7, score = 100 // f5 | cmc // 81c702000000 | add edi, 2 // 6685f1 | test cx, si // 0fadc2 | shrd edx, eax, cl // f6d0 | not al // 0f42c5 | cmovb eax, ebp // 0fc8 | bswap eax $sequence_5 = { b90a000000 5f 5e 89889c0a0000 8bc3 5b 8be5 } // n = 7, score = 100 // b90a000000 | mov ecx, 0xa // 5f | pop edi // 5e | pop esi // 89889c0a0000 | mov dword ptr [eax + 0xa9c], ecx // 8bc3 | mov eax, ebx // 5b | pop ebx // 8be5 | mov esp, ebp $sequence_6 = { e8???????? 83c408 eb02 33c0 898388050000 80be3e10000000 8945f8 } // n = 7, score = 100 // e8???????? | // 83c408 | add esp, 8 // eb02 | jmp 4 // 33c0 | xor eax, eax // 898388050000 | mov dword ptr [ebx + 0x588], eax // 80be3e10000000 | cmp byte ptr [esi + 0x103e], 0 // 8945f8 | mov dword ptr [ebp - 8], eax $sequence_7 = { 8bec 8b4d08 85c9 7413 8b8148050000 8b4024 85c0 } // n = 7, score = 100 // 8bec | mov ebp, esp // 8b4d08 | mov ecx, dword ptr [ebp + 8] // 85c9 | test ecx, ecx // 7413 | je 0x15 // 8b8148050000 | mov eax, dword ptr [ecx + 0x548] // 8b4024 | mov eax, dword ptr [eax + 0x24] // 85c0 | test eax, eax $sequence_8 = { e8???????? 8bc6 83c418 0b45e8 0f858d000000 eb78 6a02 } // n = 7, score = 100 // e8???????? | // 8bc6 | mov eax, esi // 83c418 | add esp, 0x18 // 0b45e8 | or eax, dword ptr [ebp - 0x18] // 0f858d000000 | jne 0x93 // eb78 | jmp 0x7a // 6a02 | push 2 $sequence_9 = { 869d56f9247d 9e 2490 7f7c ec 96 ac } // n = 7, score = 100 // 869d56f9247d | xchg byte ptr [ebp + 0x7d24f956], bl // 9e | sahf // 2490 | and al, 0x90 // 7f7c | jg 0x7e // ec | in al, dx // 96 | xchg eax, esi // ac | lodsb al, byte ptr [esi] condition: 7 of them and filesize < 8692736 }
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